Blow-molded drum bodies can be provided with a neck portion at one end of the barrel defining a mouth adapted to receive a cover which, like the drum body, is formed from synthetic resin and particularly a thermoplastic material.
The cover can have a portion nesting within the mouth formed with a trough outwardly of the cover bottom into which the neck of the barrel is snugly fitted. A flange or shoulder formed on the cover projects outwardly and is engaged by a tensionable clamping member which anchors this shoulder to a ring which can be applied to the drum body through the blow molding thereof and which has a T-shaped cross section. The outwardly-extending web of this T-section ring forms a second flange which is drawn toward the shoulder of the cover upon tensioning of the clamping ring.
Such barrels or drums have been widely used for the marketing, distribution and transport of chemical products and must have sufficient strength and effective sealing to resist falls, shocks and the like which may arise during transport and handling and, in addition, must have sufficient strength to enable the barrels or drums to be stacked in a full condition.
In the system of the type described in German patent document No. 36 19 367, the T-section connecting ring is located wholly below the apron of the cover and bracing of the claiming ring and of the connecting ring against one another and the cover cannot occur in an effective manner.
As a consequence, singular stresses are applied to the transition region of the drum at which the connecting ring bears upon the drum body and breakage may occur under the extreme conditions mentioned previously.
The sealing of the drum is neither reliable nor satisfactory.
The clamping ring, moreover, has its flanks or flanges, defining its U-section, of different widths so that manipulation of the clamping ring is not only inconvenient, but also time-consuming, since reorientation of the clamping ring is frequently necessary.
The cover-fixing assembly described in German patent document No. DE-OS 25 44 491 does not use a connecting ring of the aforedescribed type, but rather forms the neck in one uniform structure which fits tightly in the trough of the cover. The counterflange with respect to which the cover is anchored by the clamping ring is here formed during the blow-molding process.
Naturally the need for a relatively massive flange which must be formed by compaction of the blow-molded drum wall poses problems in fabrication and limits the thickness of the counterflange since practical considerations required that this thickness be no more than twice the wall thickness. In any event, weakened regions develop in this system at the transition zone between the neck of the drum and the drum body.